Variable-speed code-training devices



1956 J. H. HICKEY ETAL 2,772,326

VARIABLE-SPEED CODE-TRAINING DEVICES Filed July 29 1952 2 Sheets-Sheet 2 INVENTORS Lou/5 M. M/TTELSDORF :8 JOHN H HlCKEf 0 BY 6 04m dm fine/R /7 7 RNEYS United States Patent "ice VARIABLE-SPEED CODE-TRAINING DEVICES John H. Hickey, Port Washington, and Louis M. Mittelsdorf, Amityville, N. Y., assignors, by direct and mesne assignments, to the United States of America as represented by the Secretary of the Navy Application July 29, 1952, Serial No. 301,472 6 Claims. (Cl. 178--115) This invention relates to code-training devices and is directed particularly to a device, controlled by a tape containing punched intelligence, which translates the intelligence into audible signals at a given constant speed while automatically injecting additional adjustable silent periods between each letter,number or word.

The general'principle of transmitting code characters at a high rate of speed and injecting additional silent periods for training purposes is not new. In the past, characters were punched on a standard Wheatstone perforator, commonly used in the art, and longer space periods were actually punched into the tape. This methodrequired a separate tape for each efliective keying speed.

Another method has been the use of a standard tape having normal space periods with a translating device operative to cause every second, third or fourth character to be dropped, the dropped characters constituting additional space periods. One disadvantage of such a system is that only five or six difierent keying speeds could be had with a single tape. Another disadvantage is that, because of the omission of characters, readable texts could be transmittedat only one code speed.

Accordingly, it is one object of this invention to provide a code training device using a single punched tape including means for selectively adjusting the injected silent time between characters.

Another object is to provide a training device of the character described utilizing a single control tape and operative to obtain therefrom an infinite number of effective keying speeds, whereby less and less silent time can be injected between characters as the trainee progresses in code-reading proficiency.

A further object of the invention is to provide, in apparatus of the character described, a satisfactory ratio of length of silent periods between letters and words.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is an enlarged view of a section of perforated code tape showing element, character and space relationships,

Fig. 2is a simplified, perspective diagram of the functional parts of the keying head, i

Fig. 3 is a perspective diagram of the tape drive mechanism, and

Fig. 4 is an electrical schematic diagram of the timing control circuit.

In United States Patent No. 1,939,215 issued December 12, 1933, there is shown and described a photoelectric keying head and a perforated tape for use in an automatic code training device. The present invention constitutes an improvement thereover, and therefore, only so much of a keying head and tape such as is disclosed in said patent is described herein as is deemed adequate to afford a complete disclosure of the present invention.

.Fig. 1 of the drawings illustrates the code tape on 2,772,326 Patented Nov. 27, 1956 which a message is punched, as by means of a standard Wheatstone perforator. The small center holes 10 engage the teeth of a star wheel 12 (see Figs. 2 and 3), which rotates to pull the tape through the keying head, indicated generally by the number 14. As the tape is drawn through the keying head, light from an exciter lamp 16 passes through the larger holes 18, above the center of the tape and excites a tone-on photo-tube 20 to provide a tone on electrical impulse. In a similar manner, light from an exciter lamp 22 passes through the lower holes 24 in the tape to excite a photo-tube 26 which produces a toneolf electrical impulse.

Two pairs of focusing lenses 28, 34 and 32, 30 are provided in the keying head 14 to concentrate light from the exciter lamps 16 and 22 into two bright beams, one falling on each of a pair of laterally displaced slits 36, 38 in a tape retaining plate 40 along which the tape is drawn. These lenses focus the light that passes through the holes 18, 24 in the tape, through the slits 36, 38 in the tape retaining plate 40, and through holes in a rotating cylindrical shutter 42, onto the photo-tubes 20, 26. The shutter 42 is provided with a set of six tone-on holes 44, and six tone-01f holes 46. These holes are staggered evenly so that, as the shutter 42 revolves, first an on hole 44 comes beneath the center of the on aperture slit 36, and then an ofi? hole comes beneath the center of the off aperture slit 38. Consequently, light from both on and off holes 44 and 46 does not pass through and reach the phototubes 20, 26 at the same time, but alternates, and then only in pulses. Fig. 2 shows the beam of light from the exciter lamp 16 reaching the tone-on photo-tube 20.

In automatic code transmission, the dots, dashes and spaces occupy a definite length of tape, as shown in Fig. 1. A dot or a dash is called an element. Transmission of either a dot or a dash includes the time during which the audible tone is on and also a portion of time in which the tone is off. On the code tape, a dot occupies the distance between two center drive holes 10. This distance is further divided into two smaller equal units called bands. For transmission of a dot, the first baud of tape travel is the tone on time, while the second hand is the tone off time. The dash, when transmitted, has three bands of tone on time, and one band of tone-01f time as indicated. In the drawing, shaded sections indicate tone-on time, and unshaded sections indicate tone-01f time.

A character is the combination of dots and dashes that constitutes a letter, number, punctuation mark, or other symbol.

A spacing unit is the period of silent time between characters and words. It is separate from that baud of space associated with the elements. As indicated in Fig. l, the single unit of space between letters occupies two bands of tape travel; the triple unit of space between words requires six bands of tape travel.

The tape drive mechanism (see Fig. 3), comprises an electric motor 46 having an output shafit 48 coupled through a flexible coupling member 50 to the driving clutch member 52 of a clutch assembly indicated generally by the number 54. cooperatively disposed with respect to the driving clutch member 52 is a moving clutch member 56 supported on the shutter drive shaft 58 which is journalled in a bracket 60. The facing ends of the driving clutch member 52 and the moving clutch member 56 have saw-tooth serrations, as indicated by the numbers 53 and 55, respectively. The moving clutch member 56 is longitudinally slidable on its shaft 58, but not rotatable with respect thereto, by virtue of an ordinary longitudinal key and keyway interconnection, not shown. Rotatably disposed in an annular reference. number 88.

groove in the moving clutch member 56 is a collar 62 having a pair of opposed flat surfaces 64 within which are located the ends of a pair of armature arms 66, 68 of a control relay 70. The relay 70 is normally held at open position by action of a spring 72, whereby the moving clutch member 56 is held retracted from engagement with the driving clutch member 52. When the relay 70 is energized, by a circuit hereinbelow described, the armature arms 66, 68 are drawn in, carrying with them the moving clutch member 56 to bring it into engagementw'ith the driving clutch member 52. Gear mechanism 73 operatively interconnects the shutter drive shaft with the star wheel 12 so that they always rotate at proper relative speeds to produce the tone on and tone off impulses in accordance with the intelligence perforatedon the tape. The speed of the motor 46, and the lateral spacing of perforations on the tape are such that when-the clutch assembly 54 is in engagement, code is transmitted at a speediof about twenty words per minute.

Additional'time or space periods between characters 'and words is inserted at lower rates of code transmission by intermittent deenergization of the control relay 70, as hereinbelo-w described.

"A toothed clutch stop member 74 fixed to the bracket 60 is provided to engage the toothed outer portion of the moving clutch member 56 in order to prevent coasting or uncontrolled motion of the tape while the clutch is in disengaged position.

The photo-tubes 20, 26 are electrically connected, in a manner known in the art and therefore not detailed herein, so that the tone-on photo-tube 20 produces a negative voltage pulse and the tone-off photo-tube produces a positive voltage pulse. Thus, the output volttage curve of the photo-tube circuit, when transmitting the first character A of the portion of tape shown in Fig. 1, will appear as a train of voltage pulses as indicated by the number 78 of Fig. 4. This voltage pulse train is fed through .an amplifier 80 into a locking circuit .82 operative to produce positive output voltage pulses of substantially square waveform of width equal to the distance between .the tone-on and tone-off pulses. The output wave-form of the locking circuit is indicated by the reference number 84. Such locking circuits are commonly known in the electronics art and therefore not further described herein. The square-wave pulse train acts as a gate to control the output of a tonev generator 86, such as by unbiasing a vacuum tube norm-ally biased to cutoff, which vacuum tube controls the output audiofrequency voltage of the tone generator to a loud speaker 87. Such gate control circuits are also well known in the electronics art and therefore not described herein in detail.

A timing-control circuit, indicated generally by the number 89, regulates the tape movement through-the keying head 14 by intermittently energizing the control relay 70. This circuit is actuated by the pulse-train output voltage of. the locking circuit 82, indicated by the It is to be noted that the output voltage of the locking circuit 82 which is the input 'voltageto timing-control circuit, is in phase with respect to the input voltage to the amplifier from the keying head photo-tubes.

In the embodiment of this invention, the timing-control circuit 89..is..inoperative at 20 words per minute (W. P. M.) because control relay 70 is continuously energized by grounding the grid of pentode or control relay tube 94.

-Moving clutch member 56 is held against the teeth of driving clutch member 52 and star wheel 12 rotates, drawing the tape through the keying head at the constant rate of 0.8 inch per second.

At variable code speeds between 4 to 19 W. P. M. the tape, when it travels, -..moves at 0.8 inch per second.

.To reducethe W. P. M. rate, the motion of the tape is -stopped between characters, words and spacing units.

t the pentode 94 from positive to negative.

-forward one spacing unit of two bands.

' de-energizes control relay 70 at the proper intervals and for the proper time. Coil 70, when tie-energized, permits moving clutch member 56 to snap back against clutch stop member 74, as described hereinbefore, instantly stopping rotation of star wheel 12 and tape travel.

- A negative voltage (during .tone-on time) from the amplifier is taken from the center arm of the potentiometer R1 and applied to the cathode of one section of a double-diode as shown in Fig. 4. Since. the plate of this diode is connected to :ground through the variable resistor R2, the plate becomes positive .with respect to the negative cathode. Current flows from cathode to plate of. duo-diode 90 and down to ground through resistor L2 developing a negative voltage on the grid of a triode 92. This voltage is greater than the cut-off value of triode 92 and, consequently thetube is blocked, or. non-conducting. When triode 92 is non-conducting, the voltage at the common junction of the voltage divider resistors R4 and R5 in the plate circuit of the triode becomes positive. Since the voltage at this junction point is connected'to the grid of the clutch-control pentode 94, the pentode conducts, energizing the clutchcontrol relay energization coil 96 in its plate circuit, and the tape moves through keying head 14.

' A tone-01f voltage pulse from potentiometer R1 causes the cathode of the first section of the double-diode 90=to become positive with respect to its plate, and the tube ceases to conduct. Although the tone is now off,

the tape travel continues because the negative voltage applied across the variable resistor R2 has charged the condenser C1 connected in parallel therewith. This negative voltage, applied to the grid of the triode 92, holds that tube at cut-off until the condenser charge leaks off and falls below the cut-off value of the tube; it then conducts, switching the voltage to the grid of This cuts on relay-control pentode 94, de-energizes the clutch coil 96,

and halts tape travel.

The triode 92 has a fixed cut-01f value, consequently,

-the greater the negative voltage applied across'the resist or R2 during tone-on time, the longer time will be required for that voltage to fall to the conduction'point after the tone goes oif. Adjustment of the potentiometer R1 varies this applied voltage. set at'that point which applies a voltage sufiicient to hold The potentiometer is the relay coil 96 energized until the tape has traveled the distance of one baud after the element tone-on time. When the band of tape travel has passed, the clutch c'oil'96 becomes de-energized and tape travel stops for a period of dead time unless, of course, thetone on pulse of a following dot or dash keeps the relay .coil energized.

When the tape stops, it will not travel again until the clutch coil 96 is re-energized, or until triode 92is cut ofi by a negative voltage pulse generated by a. relaxation "oscillator portion of the timing control circuit '89 hereinbelow described, which drives the grid of. the triode '92 to cut-off. This negative voltage, indicated by the number 98, is applied to the second or lowericathode of the double diode 90,- producing current flow from said plate to its cathode, through variable resistor R2. and ground, developing a greater than cut-off voltage at the grid of the triode 92.

' The function of the negative relaxation oscillator volt- 'age '98 developed across the variable resistor R2 is to 'hold the triode 92 cut off and. thus energize the clutch coil 96 for the period of time required to move the tape This voltage is a sharp saw-tooth pulse. Its shape is not important,

however, because the proper period of voltagedecay time is controlled by adjustment of,the.variable resistor R This'adjustrnent changes the RC time constant of parallehconnected variable resistor R1 and condenser C1, and, consequently, the time required for the sharp voltage pulse 98 from the relaxation oscillator to leak ofi to ground. When this voltage reaches the cut-off value of the triode 92, that tube conducts and de-energizes the clutch coil 96, as hereinabove explained, thus stopping the tape after one unit of space travel.

When the tape stops for dead time between words, a single pulse from the relaxation oscillator moves the tape forward one spacing unit of two bands. At this point the triode 92 conducts again and the tape travel stops, inserting a second period of dead time. At the end of the third spacing unit between words, the tone on pulse energizes the clutch and the tape travels on into transmission of the next character.

The relaxation oscillator is a two-tube flip-flop RC oscillator comprising triodes 100 and 102. This type of oscillator operates as an over-biased multivibrator which has a stable state in which the oscillator remains, unless disturbed by a sudden input voltage of proper polarity. Application of a triggering voltage causes the oscillator to go through an unstable state and then return to the stable state, in which it remains until another triggering pulse or voltage is applied. It is the unstable state that supplies the sharp pulse 98 of negative voltage to the second or lower cathode of double diode 90.

Normally, the triode 100 is cut off when the clutch is engaged, and therefore the oscillator is inoperative. When the clutch is disengaged after the baud unit at the end of a letter, or between spacing units, the triode 100 is triggered by applying the positive voltage which appears at the common junction of the voltage divider resistors R7, R3 in the plate circuit of triode 104.

A cycle of operation will be traced, starting with the relaxation oscillator inoperative, that is, with the triode 100 out ofi, as during a tone-on period. Under this condition, the triode 100 draws no current through its plate load resistor R9, but the grid of triode 102, which is connected to that plate, draws current through resistor R9, reducing the voltage at the grid to about +150 volts. The cathode potential of triode 102 is about the same voltage. During the tone-on portion, triode 102 conducts, but a high resistance R11 in the cathode circuit limits the plate current How in the tube to a very low value, and triode 102 acts as a high resistance to ground. Consequently, the voltage at the common junction point of the voltage divider resistors R12, R13 in the plate circuit of triode 102 becomes approximately +50 volts with respect to ground.

One side of the capacitor C3 is connected to the +290 volt supply and the other side to the cathode of triode 102. Since the cathode is at +150 volts, capacitor C3 becomes charged to the difference potential of 140 volts. When the clutch is de-energized, a positive voltage is applied to the grid of triode 100 allowing it to conduct. When triode 100 conducts, the voltage at the grid of triode 102, which is connected to the plate of triode 100, drops to about +30 volts.

Triode 102 is then cut off; and its cathode voltage, due to plate-current flow through resistor R11, vanishes. However, capacitor C3, which has been charged to 140 volts, now has 290 volts applied across it, and new charging current flows up through cathode resistor R11, holding the cathode at a positive value sufficient to keep the triode 102 cut oif. As the voltage across capacitor C3 rises, both the charging current through R11, and the voltage at the cathode decrease until the cathode potential reaches the conduction value of the tube.

When the triode 102 starts to conduct, plate current fiows through the resistor R11, and the cathode voltage, due to plate current, rises an additional +30 volts. The voltage across the capacitor C3, plus that across the resistor R1 is now greater than the 290 volt supply, and the capacitor discharges back down resistor R11. At this instant the plate-current flow up through resistor R1 is cancelled by the capacitor current down and the potential difierence across resistor R11 drops to zero. In effect, this grounds the cathode, maximum current flows through the triode 102, and the tube acts as a shorting switch across the voltage-divider circuit comprising the resistors R12 and R13, driving the voltage at their mutual junction point sharply negative. At the same time, the sharp voltage drop at the plate of triode 102 is passed back through the coupling capacitor C2 to the grid of the triode 100, cutting oil? that tube. a

The negative pulse at the junction of resistor R4,, and R5 is applied to the second lower cathode of the double-diode 90. Current flows up through R2, triode 92 is cut off, the clutch coil 96 is energized, the triode 104 conducts, and a negative voltage appearing at the junction of voltage divider resistors R7 and Rs in the plate circuit of triode 104, holds the triode 100 out off. Thus, the relaxation oscillator is held in the off state until the voltage at the grid of triode 100, connected at the junction point of the divider resistors R7 and Rs, again goes positive.

During spacing intervals occurring at the end of a letter, word, or spaces between them, there are no holes in the tape. Since no pulse of light can reach the phototubes to energize the amplifier 80, the charge on the capacitor C1, due to the negative pulse from the relaxation oscillator, leaks 01'1". At the instant that the volt-age across the capacitor C drops to the conduction point of the triode 92, the pentode 94 and the triode 104 are cut off and the voltage at the grid of triode 1100 becomes positive; triode 100 is then turned on and the cycle starts again.

Adjustment of variable resistor R2 determines how long the triode 92 remains cut off, how long the clutch coil 96 is energized, and, consequently, how much tape travels through the keying head 14 during this spacing period. The variable resistor R2 is adjusted to permit a minimum of two bands of tape to travel during a spacing unit.

After the clutch is de-energized, the value of the variable resistor R11 determines how long the: capacitor C3 will take to charge up and how long before the voltage across the resistor R11 falls to conduction value of the triode 102. During this period of charging, the tape is motionless. Consequently, adjustment of the variable resistor R11 controls the amount of dead time between letters and words. By proper selection of circuit element values, effective keying speeds of from about four to twenty words per minute can be attained with a single tape by adjustment of the variable resistor R11.

The following values of circuit elements comprising the timing control circuit have been found to be satisfactory in a practical embodiment of the invention:

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention can be practiced otherwise than as specifically described. What is claimed is:

4 1. Training apparatus, comprising a movable tape having spaced indicia corresponding to intelligence; meanstranslating said indicia into signals and translating the latter-in a form receivable by a trainee for identification; said translating means comprising-a drive wheel adapted to'advance said movable tape, a drive motor, and a clutch member between said' drive wheel and said drive motor, said clutch member'being operable selectively to engage or disengage said drive motor relative to said drive wheel; and means responsive to-=the occurrence of a space between adjacent indicia of said tape for actuating said clutch member to disengage said drive motor for a predeterminedlength of=-time,-and to engage it again at the end of said predetermined length of time.

2. The apparatus as in claim 1 further comprising means for. controlling the duration of said predetermined time, whereby the word rate of transmission of the intelligence to the-trainee can be controlled.

3. The apparatus as in claim 1 wherein said clutch member actuating means comprises a timing circuit comprising an R-C network adapted to be charged during the interval that indicia are translated, and discharged during the interval between adjacent indicia.

4. The apparatus as in claim 1 wherein said clutch member actuating means comprises a generator for providing a pulsed signal of adjustable pulse-repetition frequency, individual pulses thereof being operable to initiate actuation of said clutch member into engagement after a lapse of a predetermined time interval.

5. Training apparatus comprising a movable tape record having thereon spaced indicia corresponding to intelligence, means translating said indicia into signals and transmitting the latter in a form receivable'by a trainee for identification means responsive to the occurrence of-a space between adjacentindicia for interrupting the movement of said record for a predetermined time, said interrupting means comprising a timing circuit comprising an RC network adapted to be charged during the interval that indicia are translated and discharged during the interval between adjacent indicia, and means operable to initiate the movement of said record at the end of said predetermined time.

. Training apparatus comprising a 'movable tape record having. thereon spaced perforations corresponding to intelligence, saidperforations including tone-off and tone-0n perforations means translating said perforations into signals and transmitting the latter in a form receivable by a trainee for identification, means responsive to the occurrence of a space between a tone-01f and a tone-on perforation for interrupting the movement of said record for a predetermined time, said interrupting means comprising a timing circuit comprising an R-C network adapted to be charged during the interval that perforations are translated and discharged during the interval between tone-01f and tone-on perforations, and means operable to initiate the movement of said record at the end of said predetermined time.

References Cited in the file of this patent UNITED STATES PATENTS 1,343,754 Woodland June 15, 1920- 2,293,629 Rowe Aug. 18, 1942 2,419,292 Shepard Apr. 22, 1947 2,702,313 Andrews Feb. 15, 1955 

